Effect of TLR2 deficiency on isotype distribution in OspA-vaccinated C3H/HeJ mice. Sera collected from OspA-vaccinated wild-type (WT) and TLR2−/− C3H/HeJ mice 1 week following secondary immunization were assessed for OspA-specific IgG1 (A), IgG2a (B), IgG2b (C), IgG3 (D), IgM (E), and IgE (F) by ELISA on OspA-coated plates.